Many waste treatment processes utilize thermal energy to break up waste materials into their constituent elements or more desirable compounds. The use of thermal energy to break down materials is referred to generally as pyrolization. Molten or liquid phase metals have also been used to react with certain waste materials in order to produce more desirable compounds or reduce the waste to constituent elements. In particular, liquid aluminum has been used to react with halogenated hydrocarbons and produce aluminum salts. U.S. Pat. No. 4,469,661 to Shultz described the destruction of PCBs and other halogenated hydrocarbons by contacting the hydrocarbon vapor with liquid aluminum. The aluminum was contained in low-boiling eutectic mixtures of aluminum and zinc or aluminum, zinc, and magnesium. Shultz also suggested eutectic reactant mixtures containing iron, calcium, and other metals. U.S. Pat. No. 5,640,702 to Shultz disclosed a liquid metal treatment for wastes containing radioactive constituents. This patent to Shultz disclosed using lead in the liquid reactant metal as a chemically active material for reacting with non-radioactive constituents in the waste to be treated.
U.S. Pat. No. 5,000,101 to Wagner disclosed a process for treating hazardous waste material with liquid alkaline metal alloys. The liquid metal alloy comprised approximately 50% aluminum, 5% to 15% calcium, 5% to 15% copper, 5% to 15% iron, and 5% to 15% zinc. U.S. Pat. No. 5,167,919 to Wagner disclosed a reactant alkaline metal alloy composition comprising between 40% to 95% aluminum, 1% to 25% iron, 1% to 25% calcium, 1% to 25% copper, and 1% to 25% zinc. The '919 Wagner patent also disclosed that magnesium could be substituted for calcium. In both of these Wagner patents, the waste material was reacted in the liquid alloy held at about 800 degrees Celsius.
In the process disclosed in the above-described Wagner patents, chlorine atoms in the waste material were stripped from the waste compound primarily by the highly reactive aluminum in the liquid reactant alloy. The aluminum and chlorine combined to form aluminum chloride. Carbon from the original waste compound was liberated either in elemental form or as char (CH, CH2, or CH3). Both the aluminum chloride and liberated elemental carbon sublimed to a gaseous state at the 800 degree Celsius. reaction temperature and were drawn off and separated.
Many hazardous waste sites have different types of wastes mixed together. The mixed waste may include numerous different types of halogenated hydrocarbons, other non-radioactive wastes, and radioactive isotopes. These mixed wastes which include radioactive and non-radioactive materials have proven particularly difficult to treat. Although, many non-radioactive wastes may be treated chemically and broken down into benign or less hazardous chemicals, radioactive constituents of the mixed waste stream cannot be manipulated to reduce or eliminate their radioactive emissions. It is desirable to separate the radioactive constituents from the other materials in the mixed waste and place the radioactive constituents in an arrangement for safe, long term storage.
Storing radioactive waste poses several problems in itself. For a radioactive isotope which has a long half life, a quantity of the material remains radioactive for many years. Thus, a storage arrangement for this long-lived radioactive waste must be capable of securely holding the waste for a very long period of time. However, radioactive emissions, particularly alpha radiation, can interact with the material of a container intended to store radioactive waste. This interaction can cause the container to degrade relatively quickly, long before the radioactive waste itself has degraded.